We machined the fittings for the poseidon water rocket in the student workshop of our university.
After turning the two fittings in a lathe, boring the axial holes and cutting the axial theads, we milled the sides and drilled the radial holes.
The left fitting connects the main valve (inner thread, G1/4) to the water tank (outer thread, G1/4) and depress valve (radial hole, G1/8).
The right fitting connects the quick disconnect adapter (radial hole, G1/8) to the air tank (outer thread, G1/4), and has thread (M8) for the parachute eyebolt.
Down below are the technical drawings for the machined fittings.